I have never felt compelled to leave a Google review of a movie before, but this was so abhorrent that here I am.
I went into this film with high hopes, as it's James Wan and he knows his way around a horror film, and boy was I disappointed! The plot of this film feels like it was thought up by someone coming round from anastheasia after a wisdom tooth surgery, who then refused to take any follow up questions when they were sober.
In my opinion, the only redeeming feature of this movie was some of the actors. The writing relied too heavily on tropes, clichés and poorly thought through ideas. Save yourself 1 hour and 51 minutes of your life, and watch something else.
SPOILERS FROM THIS POINT
This film needed to pick a lane. Was Gabriel a teratoma using Madison's body, or was he an evil entity from the depths of Hell? Because they seem to have put a lot of effort into the parasitic twin angle, but that leaves far more questions than answers. Why does Maddy have superhuman strength as Gabriel? Why can he seemingly control electronics? How does he have such excellent control of a body he's using backwards? How do you explain the phone call to the detective when Maddy is in the interrogation room with him? None of these have even the beginning of an answer. If we're to believe there's supernatural abilities at play, why has this never effected Maddy before? Why even bother with the parasitic twin thing, when he could just have been a demonic "imaginary" friend? These and more questions would plague my mind, if this film were actually interesting enough to warrant thinking about for more than 10 minutes.
It's rare that a film is bad enough that I actively discourage people from even giving it a go, but Malignant has made that list.